1. Field of the Invention
This invention relates generally to a device, usually of some rigid material, for strengthening or supporting objects or fastening them together, for example, a C-clamp.
2. The Prior Art
The prior art is exemplified by an appliance with opposite sides or parts that may be adjusted or brought closer together to hold or compress something. A so-called bar clamp has a longitudinally extending bar which may be notched and grooved so that an anvil may be adjustably positioned along the length of the bar. At one end of the bar, there is an upstanding bracket through which a threaded rod extends in threaded relation therewith. The rod may be selectively rotated by turning a crank arm on one of the ends of the rod. At the opposite end of the rod, there is a pad which is also slidably supported by the bar. Thus, by turning the crank, the rod will threadedly advance or retract in the bracket, thereby correspondingly advancing or retracting the pad towards and/or away from the anvil so that objects may be held or clamped thereby.
In another form of prior art device, a C-clamp is provided wherein a body portion is made of a rigid material such as metal and is shaped in the form of the letter "C", i.e., it has a bight portion from which extend longitudinally spaced apart parallel arms disposed at right angles to the bight portion.
One of the arms has a threaded aperture through which extends a correspondingly threaded rod having an actuating lever on the free end thereof. The other of the arms has an anvil portion formed thereon against which a workpiece, or, a part to be held or clamped may be retained when engaged by the end of the threaded rod between the arms.
To enhance the engagement of the rod with the workpiece, there is oftentimes provided a pad so that the workpiece does not become deformed or otherwise damaged by the clamping or holding action. When such a pad is provided, it is sometimes retained on the end of the threaded rod by a ball joint, or simply by; some simple form of slip joint so that the pad may accommodate relative rotation with respect to the rod.
However, as clamping forces increase, the pad tends to rotate along with, or in unison with, the rod and the workpiece is apt to be marred or damaged during the course of the clamping or holding action. With the C-clamps available on the market today, many times the friction in the ball joint will be greater than the friction between the pad and the clamped workpiece, thereby causing the pad to move and loosen up, particularly on non-parallel objects.